Defroster control



March 26, 1968 R. H. THORNER DEFROSTER CONTROL l 2 Sheets-Sheet Original Filed July 19, 1960 s g2b INVENTOR. @055/27 EOP/vf@ C35 DEFROS TER CONTROL Original Filed July 19, 1960 2 Sheets-Sheet 2 United States Patent C 3,374,643 DEFROSTER CONTROL Robert H. Thorner, S750-F W. Chicago Blvd., Detroit, Mich. 48204 Application Feb. 3, 1964, Ser. No. 342,216, now Patent No. 3,321,928, dated May 30, 1967, which is a continuation of application Ser. No. 43,825, July 19, 1960. Divided and this application Oct. 24, 1966, Ser. No. 588,915

30 Claims. (Cl. 62-140) ABSTRACT OF THE DISCLOSURE The main disclosure in this patent comprises a fluid (air) pressure circuit including frost-sensing valve means mounted a predetermined distance from a cooling surface corresponding to the thickness of frost formed on the cooling surface and also includes a pressure-responsive member for operating the control means (such as a switch) for regulating defrost heat, and further includes This application is a division of application No. 342,216 filed Feb. 3, 1964, now Patent No. 3,321,928, issued May 30, 1967, which, in turn is a continuation of application No. 43,825 filed July 19, 1960, now abandoned.

The present invention relates primarily to a control mechanism for refrigeration apparatus and particularly to a control device for controlling the formation and reduction of ice on a cooling unit, such as for defrosting systems of refrigerator apparatus. In a broader aspect, the present invention may be employed to control the thickness of formation of any substantially solid material on (or in) any solid base, such as on a tube, rod, etc.

In numerous refrigerating systems, means are provided to control the build-up and elimination (or reduction) of ice or frost which may form on the evaporator. These systems often include heating means to remove or reduce such formation of ice. In certain types of commercial refrigeration such as ice-bank systems, as well as in some defrosting systems, such removal means comprises merely a switch to turn the compressor off so that the ambient heat eventually diminishes the ice coating on the evaporator. For purposes of this disclosure, ice and frost can be considered synonymously.

Defrosting control systems are used to remove the frost which forms on the usual evaporator coils as well as on other parts or on food adjacent thereto in a refrigerator. Such frost is highly undesirable since it acts as an insulator for the normal extraction of heat from the food compartments to the cooling unit thereby reducing the efficiency thereof. Accordingly it is desirable to remove the frost quickly without melting the food, ice cubes, etc. Hence it has been rather common practice to provide additional means to intermittently apply heat to the evaporator and adjacent parts to periodically remove such frost rapidly and automatically. Such defrosting means usually comprise a separate electric heater element adjacent the evaporator coil or a solenoid-operated valve which acts to pass the compressed refrigerant (such as freon) directly from the compressor to the evaporator while bypassing 3,374,643 Patented Mar. 26, 1968 ice the condenser and capillary tube of the refrigerant circuit. The present invention is concerned in the forms shown, with the means to control the thickness of formation or accumulation of ice or frost on the surface of any of the refrigeration systems above referred to. The present invention is more specifically concerned, by way of example, with control means for initiating and terminating the intermittent action of the defrosting means of a refrigeration system.

The presently known defroster control devices provide manual or automatic means to initiate the defrosting action. The manual means usually comprises a 'push button so that initiation depends upon human decision. The presently used automatic initiating means frequently cornprises a clock mechanism to start the defrosting action after a definite time interval, such as twenty-four hours, or after a predetermined total running time of the compressor, such as twelve hours, for example. All present defroster control devices provide automatic means to control the duration (or termination) of the defrosting action. Such terminating means usually comprises a gas-filled bellows-type thermostat to shut off the defroster action when the temperature in the controlled food compartment rises to a predetermined value. However, sometimes clock mechanisms are also used to control duration.

A novel lmeans for terminating the defrosting action which senses ice formation is disclosed in the above-referred to patent, and the present invention relates to improvements in the invention therein claimed.

Defroster control devices in recent years have become widely used in domestic refrigerators having a food freezer section that is separate from the so-called refrigerator or fresh food section. The freezer section in such refrigerators is provided with a fan to circulate air over the evaporator coil and the frozen food products. With this construction and with intermittent defrosting of the freezer evaporator, frost never forms on the food, and melted frost from the evaporator coil is disposed of automatically.

It has always been important to terminate the defrosting action as soon as all of the frost melts in order to prevent unnecessary heating of the food compartments and possible melting of frozen foods therein. However the initiation of the defrosting action has not been too critical in refrigerators that lower the temperature only slightly below freezing `such as to 25-28" F., -as in the fresh food compartment. But when defrosting the freezer sections of refrigerators having two food compartments, control of initiation is somewhat more critical. This is true since near-zero degree temperatures are maintained in the freezer section to assure rapid freezing of foods placed therein, and to assure that the desired freezing is not hampered by insulation produced by excessive formation of frost. This problem is even more severe because of the loss in efficiency ca-used by transferring heat twice; the heat rst is transferred from the food to the circulating air, and secondly from this air to the evaporator.

Neither the initiation nor termination of a defrosting cycle, if correct, should `be a function of time alone. Much worse, clock mechanisms not only are complex and costly but are very unreliable and are likely to become so noisy as to require replacement.

For termination of the defrosting cycle, gas filled bellows which sense only temperature are not only costly, but the gas therein is adversely affected by variations in air density. Accordingly, altitude or air density compensation means frequently are provided to `compensate for the low atmospheric pressures such as normally exist at Denver, Colo., for example.

tively longtime without deterioration. It has been found that some of the present defroster controls which sense only temperature act to turn oif the frost-destroying heating element too soon if the frost formation is heavy and if the calibration has been established on the basis of a light frost accumulation.

In those applications in which the -controlled material is fragile or friable, such as frost, the past attempts to mechanically sense the thickness of such friable material (frost) have required that the sensing member applies a force against the material (frost in the examples herein) Ywhich tends to crush or deform the surface thereof; this action, in turn, tends to produce inaccurate or inconsistent results.

Secondly, in some of the past attempts to mechanically sense the thickness or amount of material forming on a base, as above discussed, the control means (which usually includes means such as an electric switch) is moved gradually as a function of the formation of the material.

In this instance, the operation of the electric switch iscritical since the snap -action must be set carefully to correspond exactly to the correct thickness of material.

A broad object of the present invention is to provide a simple and novel mechanism to control the amount or thickness of formation of any substantially firm or solid material on any solid base.

Another object of the present invention is to provide a mechanism to control the amount or thickness of forma- Ytion of any material on a surface or base as described in tion of any material on a surface or base, as described` in either of the preceding two paragraphs, in which the control means is operated only after the material forms to substantiallyV the desired predetermined amount or thickness.

A most important object of the present invention is` to provide a mechanism to control the amount or thickness of any material on a surface or base as described in any of the preceding paragraphs in which means are provided toproduce a relatively small amount of energy, and integrating means are provided to store the energy over a period of time to be released periodically for providing the large amplied force for actuating the control means.

A primary object of the present invention is to provide in an .automatic defroster control device simple, inexpensive, quiet, trouble-free and consistent duid-operated means to effect initiation of a defrosting system by a direct measurement of the thickness of the frost formation.

VAnother-object of the present invention is to provide an automatic defroster control for a refrigerator having fluid operated means to initiate the defrosting action as a function of the thickness of frost formation, and having means to terminate the defrosting action which is dependent on the melting of a specific body of ice.

A further object of the present invention is to provide in an automatic defroster control system novel means to control the duration (and termination) of the defrosting action including a sensing member immersed in a vessel in the ow path of melted frost and including means to initiate the defrosting action when first, starting l the refrigerator after installation and before the icecontaining vessel is filled with water.

Other objects and advantages of the invention will become apparent from the following description and from the accompanying drawings, in which:

FIG. l is a somewhat diagrammatic illustration of a refrigerator having a freezer section with the device of the present invention shown in its operative relation to the several components of the refrigerator;

FIG. 2 is an elevational view of a device (with its cover removed) for controlling the duration of the defrosting action and for terminating same;

FIGS. 3 and 3a show somewhat diagrammatic partial sectional views of one form of the control device of the present invention in which the source of fluid pressure for initiating the defrosting action is produced by opening or closing of the refrigerator door;

FIG. 4 is a sectional view along the line 4-4 of FIG. 3 showing -my improved ice sensing means for terminating the defroster action;

FIGS. 5 and 6 are fragmentary views of the device of FIG. 3 illustrating modified means to sense the formation of frost;

FIG. 7 is a diagrammatic view of a modified power means using a source of energy for initiating the delfrosterV control in response to changes of pressure of the refrigerant;

FIGS. 8, 9, 10 and 10a are somewhat diagrammatic partial sectional views of other forms of the initiating system yof the present invention in which the force for initiating the periodic deirosting action is produced by means energized by electro-magnetic or thermal means;

FIG. 11 is a diagrammatic view of a' modified form of the invention showing novel energy integrating means toV provide periodic large forces for initiating the defrosting action witha relatively small energy source; and

FIG. lla is a diagrammatic view, with parts in section, of a modified form of electro-magnetic initiating means.

It is to be understood that the invention is not limitedV a control device to effect a change in condition, such as -bulk or thickness, of any firm or solid material such as frost for example. I provide control means for regulating the change, such as a switch in an electric circuit, and actuating means normally movable independent of the control means and disposed to operateV same periodically. I provide sensing means mounted at a predetermined relationship with respect to the material and movable in relation thereto (intermittently) in response to the periodic movements of the actuating means. The sensing means is disposed to prevent the actuating means from operating the control means whenever the intermittent movements of the sensing means is'not blocked or 'prevented by the bulk or mass Vof the material; but whenever the intermittent movements of the sensing means is blocked or prevented by the bulk of the material,v the actuating means can then operateV the control means.

In addition, the lforegoing combination may be arranged for those applications in which the material is friable or fragile (such as frost), to provide that the force of the movable sensing element acting on the friable material is substantially less than the force of the actuating means for operating the control means; so that the force of the sensing means does not crush or deform the materialto cause inaccurate or inconsistent results. In this action, the control device provides an action similar to any uid or electric servomechanism.

n accordance with the specific form of the invention shown herein, I provide an automatic defroster control for a refrigeration machine in which the detrimental factors of present controls such as high cost, complexity, excessive noise, unreliability, inconsistency, and variations with air density are eliminated, and which will initate the defrostng action after a predetermined thickness of frost is formed, and will melt substantially all the frost (without melting the frozen foods) and then terminate the defrosting action. I provide such desirable initiating action by utilizing a uid (pneumatic) system or circuit using air as a medium in which the actuating means includes a pressure responsive member disposed to initiate the defrosting action and to actuate or set the means to control the duration of the defrosting action. I further provide in one form of my invention valve means for closing said fluid system, which comprises the sensing element of the sensing means. The valve means is mounted a predetermined distance from a portion of the evaporator such that progressive formation of frost gradually reduces the possible degree of valve opening. I also provide a source of energy which is converted to fluid pressure energy in the fluid system which will periodically provide a pressure to activate the pressure responsive member only when the valve means is unable to open sufficiently to relieve such pressure by reason of the formation of a predetermined thickness of frost. In one form of the invention the source of fluid pressure comprises a pressure producin-g member energized by the -opening and closing of the refrigerator door. In other forms of my invention, I provide various other energy means as a source to provide forces for actuating the pressure producing member which means are dependent on the cycling of the compressor in some `forms of the invention illustrated herein; such energy means may includea heating element for a temperature responsive bimetal, or a heated gas-filled bellows, or a solenoid, arranged to provide relatively quick movements of the pressure-producing member. This source-energy is converted to another form of energy, such as pressure energy, to perform the defrost-controlling action described above. Although any means for controlling the duration of the defrosting cycle may be used and operated by the above-described initiating means, I have disclosed herein a novel means dependent on the melting of ice in a vessel located in the flow path of melting frost (or in other such container adjacent the cooling unit) to control this duration, which novel means has special utility when used in combination with my novel cycle initiating means.

In an important sub-combination invention, I provide a relatively small source of such ener-gy or power force to operate an integrating mechanism which stores or adds up this small energy over a period of time and releases the stored energy periodically at a force substantially larger than the original power force.

Referring now to the drawings, and particularly FIG. 1, there is shown diagrammaticaly by way of example an installation of the present invention as a defroster control unit in operative relation to a refrigeration machine and the electric circuits necessary for operation of the control unit. The entire defroster control may be considered to comprise two components. A control unit which controls the duration (or termination) of the defrosting action, as shown detailed in FIG. 2, is the iirst component; and the initiating mechanism or means, a portion of which comprises a housing 17, is the second component. In FIG. l, a typical refrigerator is illustrated having a cabinet (in dotted outline) forming a food freezer section 19 and a fresh food section 21 divided by Walls 23 and 2S. The refrigerant system includes the usual compressor C which sends the refrigerant through a tube 27 to a condenser D, thence through a capillary tube 29, to be expanded through a frozen food evaporator or cooling unit 30, where it either returns under vacuum to the compressor through tube 31 or flows to a second evaporator Sila (shown dotted) for the fresh food section 21, all in a manner well known to those skilled in the art. A conventional solenoid-controlled valve S is mounted in a tube 32 which may bypass refrigerant around the condenser directly from the compressor to the evaporator coil 30. When the solenoid valve is opened, by action of the defroster control to be described, the hot refrigerant passes directly from the compressor through the evaporator which quickly melts all the frost formed thereon. The melted frost drops into a trough 34 mounted at the back of the freezer section where the Water flows through a tube 36 to a pan 38, where the heat of the condenser helps the melted frost to evaporate. In normal operation, the contents of the freezer section are cooled by air circulated by a small air fan (not shown) which causes air to circulate around the freezer section and over the evaporator 30 and frozen food.

Temporarily referring to FIG. 2, to be discussed in detail hereinafter, the unit 15 includes an electric switch having a fixed contact 39 connected to a terminal 40, and an opposed fixed contact 42 connected to a terminal 44. A movable contact 46 is carried by an arm 48 swingable about a knife edge connection with a support 50 and is connected to a stationary terminal 52. A strong extension spring 53 is connected at one end to the contact arm 48 and at its other end to an arm 54. The switch is shown in its normal position without the defrosting system in operation, and in this position terminal S2 is electrically connected to terminal 40 through contact 46 resting on contact 39 by the force of spring 53. When arm 54 is moved to the dotted position 54 by means to be described, spring 53 is moved over center to the right, as viewed in FIG. 2, so that contact 46 snaps against contact 42 to electrically disconnect terminal 52 from terminal 40 and connect to terminal 44. In this position, however, the spring 53 maintains a relatively large force urging the arm 54 back to the full line position shown in the drawings since the position of the spring is always at the left of the fulcrum of the arm 54. When arm 54 is moved back to its original position shown, the contact 46 is snapped back to its original position shown in FIG. 2.

' terminal 52 of the defroster control unit 15. Another conductor 62 connects the normally closed pole of switch 58 to terminal 44 (FIG. 2). Also the solenoid valve S is connected to terminal 44 by wire 64 in parallel with the compressor when the circuit to the latter is closed only through the switch in unit 15.

The action of the refrigerator and defroster control is as follows. When thermostat switch 58 closes the left pole as viewed in FIG. l, with the switch of unit 15 in the position shown in FIG. 2, the compressor lowers the freezer temperature in a normal manner until shut off by the thermostat. However, when the defroster control causes arm 54 to lmove to position 54 in a manner to be described, the compressor C is operated regardless of the position of switch 58, and solenoid valve S opens the bypass line 32 to pass hot gas through the evaporator 30 until all the frost melts and is collected in pan 38 as described. After all the frost is melted, the defroster control causes arm 54 and contact 46 to return to the position shown in FIG. 2, by means to be described.

It should be appreciated that there are many possible combinations of refrigerator arrangements and circuits. For example a refrigerator may have one or two separately closed compartments; in a two compartment unit, the freezer section may be on top or below; or the defrosting system may utilize hot gas or electrical resistance units, etc. Also, the defroster control 15, 17 might be mounted in many different portions of the refrigerator, such as at the back of the freezer section between the inner or outer liner, or mounted inside the freezer compartment directly on the coil 30. In addition, the ice-thickness or defroster control device can be used for any kind of refrigerating machine, not just as a defroster control for the freezer section of a domestic refrigerator as described in connection with the principal form of the invention. Hence, the particular combination shown in FIG. 1 is merely illustrative, in which the defroster control is shown mounted between the inner liners 23 and 25 which Separate compartments 19 and 21, for controlling the frost in the freezer section 19 shown in the lower portion of a two compartment domestic refrigerator.

Now referring to FIGS. 2 4, the means to control the duration (hence the termination) of the defrosting action will now be explained. In unit 15, the mechanism is encased in a housing V68 of any suitable material such as sheet metal with three sides 68a folded up from the base. A fourth side is formed by the electrical insulating base 69 for the switch, which base has a plurality of projections 69a for insertion into holes in the sheet metal housing and cover to be secured together by upsetting portions of the sheet metal. The housingv 63 includes projections or tabs 6817 cooperating with suitable openings in a cover 70 (FIG. 3) to be staked or bent to secure the cover to the housing. In unit 15, arm 54 carries a detent member 72 hinged thereto at one end to permit angular movements of the detent in relation to arm 54. A light extension spring 74 is suitably secured at one end to arm S4 and at its other end to detent 72 urging the detent downwardly into engagement with a cam or guide member 76 which is secured to one side of housing 68'by suitable means as by staking or soldering,

A bushing member 78 includes a hexagonal ange which is secured to the inside of housing 68 by suitable means as by soldering or staking. The bushing 7 8 includes a bore to journal a shaft 8i) which carries a latch member 82 secured thereto for angular movements with the shaft.

Y A very light extension spring S4 is suitably secured at one end to housing 68 and at its other end to a portion 8217 of latch member 82 to urge same in a counterclockwise direction into the free position shown in FIG. 2. Detent 72 includes a catch portion S6 disposed to engage a latch arm 82a of latch member 82 in a manner tobe described. A rectangular shaft 90 is supported and guided by a tab 92 (struck inwardly from housing 68) for axial sliding movements to abut and actuate arm 54 as shown.

In FIG. 3, unit is shown with its cover 70 installed and the unit mounted in its operative position between inner walls 23 and 25 of chambers 19 and 21, respectively. Shaft 80 projects outwardly through cover 70 (perpendicular to the drawing) and has a sensing arm 94 secured thereto by suitable means, as by a set screw, for angular movements therewith. A small vessel 96, as shown in FIGS. 3 and 4, is suitably secured to a portion of the evaporator tubing 30 such that the vessel is below the tubing. The vessel may be made of any suitable material, but a metal such as aluminum is desirable to provide the highest heat conductivity which is facilitated by wrapping a portion 96a of the vessel around the tube. The vessel is mounted so that an offset sensing portion 94a'of arm 94 is suspended inside an ice chamber 98 formed by the vessel. A light leaf spring member 100 may be secured to arm 94, as by rivets, and is slightly pre-bent to ride against the surface of portion 96a in operative movements of arm 94 for reasons to be discussed.

The operation of the defrosting duration or termination control unit above described is as follows'. Referring to FIGS. 1-4, assume that chamber 9S of vessel'96 is completely filled with water or other freezable liquid which is frozen in normal refrigerator operation. After frost forms on the evaporator to a predetermined thickness or depth, shaft 90 'is automatically moved temporarily to the left by means to be described until arm 54 is moved to the position at 54'; This action causes contact 46 to move against contact 42 which operates the compressor and solenoid valve to send hot gas through evaporator 30 for melting and disposing of the frost in a manner previously described. At this time the ice or frozen liquid in vessel 96 is also subjected to heat somewhat by radiation but primarily by conduction fro-m the tube 30, which is the reason why a vessel made of a metal of high heat conductivity may be desirable. Also, movement of the switch arm to the position at 54 carries detent 72 leftward until spring 74 causes catch portion 86 to engage latch arm 82a. The force on shaft 90 is soon removed, as will be descirbed. Then the force of spring 53 tends to return arm 54 into the position shown with a force that easily overpowers the force of spring 34.*Such forces are transmitted through detent 72 which now abuts latch arm 82a tending to impart angular movement to latch member 82. However, such angular movements are prevented by arm 94 now abutting against the ice or frozen liquid in vessel 96 which tends to be compressed between the left edge of the sensing portion 94a and the left inside wall 96b of the vessel. Thus, the ice acts as an ice or frozen-liquidV link which grows smaller gradually as the ice or frozen-V liquid progressively melts since contact with the melting ice is maintained by spring 53. As arm 54 with its detent member 72 gradually moves rightwardly when the ice in vessel l96 melts, a cam portion V72a of the detent member contacts cam 76 which gradually raises Vthe detent member in opposition to spring 74. After a predetermined travel of arm 54 and detent 72 which is calibrated to occur when all the frostV is melted, the catch portion 86 disengages from latch arm 82a. This instantly causes Vtwo simultaneous actions as follows: the firstV action is that spring 84 instantly returns latch member 82 into the angular position shown in FIG. 2 in which arm 82h contacts the lower side of the housing; accord-V ingly the Vsensing portion 94a is moved rightwardly away from the remaining ice and restored to the position shown. The second simultaneous action is that spring 53 causes arm.54 and detent 72 to snap into the position shown in FIG. 2, which also moves the contact 46 into the position shown against contact 39. This terminating'action causes the solenoid valve S to shutoff the ow of hot gas through the bypass tube 32 so that refrigerator operation is againY normal. The compressor is again controlled only by thermostat 5S, and the ice in the vessel 96 soon freezes so that the defrostingcycle can be repeated as aboveV described after a predetermined thickness of frost is formed.

It is important to appreciate thatV all the ice in vessel 96 may not melt, but only that portion adjacent the metal surfaces such as at sensor portion 94a and the interior walls of vessel 96. The unit 15 Vis so calibrated that when all the frost on the evaporator is melted, the detent member 72 is disengaged from latch arm 82a after a predetermined travel. This can be controlled by numerous variables such as the height' of chamber 98, the thickness of metal of sensing portion 94a, the vertical adjustment position of cam 76, etc.

It -is important to appreciate that the detent travel is always larger than (and easily includes) the travel necessary to cause contact point 46 to snap between. contacts V39 and 42. Hence, the production setting of the switch snap is not in the least critical, as in many prior devices; because for production units it is only necessary to provide the relatively large travel of detent 72, such as by setting the vertical position of release cam 76.

When the refrigerator is first placed in service, the Y present invention provides novel means so that it is unnecessary to lill chamber 98 with water initially to make the defrosting 'system operative. The construction also produces a more accurate calibration since the device is arranged to sense the accumulationrof frost directly. As explained above, an abutting frost sensor such as leaf spring 100, contacts either tube 30 or vessel -portion 96a in all positions of arm 94. Also, vessel 96 is mounted below tube 30 to be in the -ow path of melting frost to keep chamber 98 completely lled, whereas the overow falls into trough 34 to be evaporated as described. As explained above, the control is calibrated to terminate the defrosting action after a predetermined melting time dependent on numerous factors includingy a completely full amount of water in vessel 96. Thus, as calibrated, if chamber 93 is only one-half full, the defrosting action would terminate before all the frost is melted.

The defrosting action is developed as follows, starting with a completely empty vessel at the time the refrigerator is -first placed in service. When the frost forms to its predetermined thickness on tube 30y (FIG. 4), a portion of the frost covers the frost sensor leaf spring 160. Then when shaft 90 is moved to start the first defrost heating action, arm 94 is moved gradually to the left by spring 53 as the frost which is abutted by leaf spring 100 melts until detent 72 disengages from latch arm 82a. The frost tends to be compressed between the leaf spring 100 and stop means, such as a tab 96C (FIG. 3) which projects transverse to the tube. In other Words, the leaf spring 100 actually abuts the frost trapped between the spring and the tab 96C. However, without water in the vessel (as calibrated), only a small portion of the frost melts on this first cycle but some of this melted frost falls into chamber 96 to cover perhaps only the end of sensor portion 94a. Then the second defrosting cycle Will be longer due to the small amount of ice added in vessel 96, so that a larger percentage of the frost is melted during this second cycle. Some of the additional melted frost again falls `in chamber 98, so that a higher percentage of frost is melted on each subsequent defrosting cycle. This action continues until the vessel 96 is completely full so that all the frost is melted during each subsequent cycle as call'- bmted. In actual operation, the Vessel is full after only the first few cycles when the refrigerator is rst placed in service. The leaf spring 100 might be omitted if arm 94 were mounted close enough to be embedded in the frost that forms on tube 30. However to accommodate production variations, the leaf spring 100, or equivalent, is provided. In any case, the calibration is partly produced by the arm 94 or leaf spring 100 compressing or abutting the frost between it and tab 96e and partly by the sensing portion 94a compressing or abutting ice between it and the wall 96b of the collecting vessel.

Tests of this concept have shown that the defroster control can be calibrated satisfactorily to terminate the defrosting action without vessel 96 by using only the direct frost sensor (leaf spring 100) or equivalent abutting means as a sensing member to entrap frost between the `sensor and projection 96C 0r equivalent stop means. However in this instance, the control device must be mounted on the evaporator coil 30 somewhat near the last portion of frost to melt. When the vessel 96 is combined with the abutting frost-sensor 100, although the cost increases slightly, the control unit can be mounted anywhere on the evaporator coil since the travel of sensor arm 94 can be calibrated to terminate the defrosting action at a position corresponding to the last portion of frost to melt, even if remote from the control device.

The principle of the duration control unit as above described, except for the automatic vessel-filling means shown in FIG. 4, is disclosed in my Patent No. 2,949,016, in which the theoretical concepts are discussed in more detail. It is important to appreciate that any duration (termination) control device may be used or operated by the novel initiating control means now to be described. However, the inherent simplicity, reliability, consistency, function accuracy, and potentially low cost of the duration control disclosed herein provides an inventive combination with the initiating means now to be described.

Now consider the means to initiate operation of the duration control device, which in the specic duration device disclosed herein, comprises the means to effect periodic or intermittent movement of shaft 90 after a predetermined amount of frost has formed. Referring to FIGS.

3 and 3a, shaft 90 is actuated by a pressure responsive member such as a single or multiple fold flexible diaphragm 102 made of any suitable material either metallic or nonmetallic such as synthetic rubber. The diaphragm is operated by air as a working medium and is secured between housing 17 and a cover 104 to form two air chambers 106 and 108. Chamber 106 is vented to the atmosphere through holes 110, While chamber 108 communicates with any source of air pressure, to be discussed, through a conduit, tube, or passage 112, which actually is a part of chamber 10S from a fluidic standpoint. A tube or passage 114 connects with passage 112 and projects through wall 23 into the freezer compartment as shown. A valve 116 normally closes the end of passage 114, and a very light leaf spring 118 is pre-bent to support and maintain valve 116 in its closed position. Leaf spring 118 is secured at one end to a fixed portion of the refrigerator, such as to a post 120, to enable swingable valve movements as leaf spring 118 bends to open valve 116 as will be discussed. Tube 114 is mounted in relation to the evaporator tube 30 such that leaf spring 118 and valve 116 is positioned a predetermined distance T from evaporator tube 30, so that these elements comprise the frostsensing portion of the invention. Passages 112 and 114 may include, in one form of my invention, another passage 122 having an inlet check Valve 124 biased closed by a hair-spring 126. It is important to appreciate that any other kind of valve construction, such as a simple ball valve, may be used in place of valve 116 and leaf spring 118 as -long as its movement can be limited by the formation of frost as explained.

Energy-responsive means are disclosed to provide a periodic source of air pressure to passages 112, 114 and 122, which means may comprise some type of pumping apparatus. 1n the form of the invention shown in FIG. 3a such pressure-producing means comprise another diaphragm assembly 128 mounted remotely from diaphragm 102 and located anywhere between the inner liner 130 and outer liner 132 to lbe adjacent the door 134 of the freezer compartment. The assembly 128 includes a diaphragm 136 preferably of synthetic rubber, although a metallic or synthetic rubber bellows might be used. Diaphragm 136 is secured between a housing 138 and a cover 140 which forms two air chambers 142 and 144. The cover 140 is secured to a wall 143 of the refrigerator by any suitable means. Chamber 142 is Vented to the atmosphere by holes 146, and chamber 144 communicates only with passage 112, such as by a long metal or synthetic rubber tube strung between the inner and outer walls of the refrigerator. A shaft 148 is guided by a bushing 150 and is secured to diaphragm 136 and biased by a spring 152 to abut door 134 when closed :as shown. The passages 112, 114, 122 and chambers 108 and 144 comprise a liuid (air) circuit, which circuit in the form of the invention shown in FIGS. 3-3a would include the sensing valve means 116, 118 and intake valve means 124, 126 and may also include, or at least be associated with, diaphragms 102 and 136 which comprise movable walls for chambers 108 and 144, respectively.

The operation of the entire initiating system is as follows. When the `door 134 is opened, spring 152 forces diaphragm 136 to its extreme rightward position which draws air through inlet check Valve 124 (valve 116 being closed) through passages 114 and 112 into chamber 144. When the door is again closed it moves the shaft 148 and diaphragm 136 quickly to its normal leftward position as shown. This action causes the intake air to be forced out at a very low pressure through valve 116 (Valve 124 now being closed) which is free to open providing it is not blocked by frost on tube 30. Hence in this action, the air pressure does not build up sufficiently in tube 112 and chamber 108 to actuate diaphragm 102 in opposition to the force of spring 53 (FIG. 2), so that at this time valve 116 acts as a relief valve. However, after frost forms on the evaporator tube 30 to a predetermined thickness T at or near the leaf spring -valve 116 the valve is blocked from normal opening by the frost. Then after the door is opened and air drawn into the system, a subsequent closure of the door causes air pressure to build up in the air circuit passages and chambers 114, 122, 112, 144 and 108 to force diaphragm 102 and shaft 90 to the left, as viewed in FIGS. 2 and 3, which moves `arrn 54 to the position 54 to initiate the defrosting action as above described. After the duration -unit 15 terminates the defrosting action when detent 72 disengages from latch Varm 32a as already explained, spring 53 causes arm 54, detent 72, shaft 90, and diaphragm 102 to snap into the position shown; and since the frost is then melted from tube 30, the air from chamber 108 is easily forced out through valve 116 by diaphragm 102, so that the Ventire cycle can be repeated.

Since frost is fragile and friable, only a very slight forcecan be applied thereon to sense its thickness with acceptable consistency and accuracy. As above discussed, the force and travel of the sensing element in my invention can be very small compared to the force and travel ofV the actuating member; and this small sensing force and travel controls the larger separate force and travel. Thus the action is similar to a fluid or electric servo-mechanism.

In this action the frost-sensing element such as the sensor V116 applies a very small force acting periodically on the frost to control the transmission of a relatively large and separate actuating force, as produced by diaphragm 136, to an actuated member, such as shaft 90, for operating the control switch. Y Y

FIG. 5 shows'a modified form of the frost-sensing portion of the invention in which the end of tube 114 itself is positioned a predetermined distance T from the evaporator tube 30 without any valve means at its end. With this construction7 which could be used with any direct measuring ice-sensin-g device, frost must build up at least to thickness T to cover the end of tube 114 before the control unit can be operated. Then when door 134 is closed, pressure builds iup in chamber 108 to move diaphragm 102, shaft 90, and arm 54 which actuates unit 15 as above described.

FIG. 6 shows still another modified form of the frostsensing portion of the invention in which the passage 122 and check valve 124 could be omitted. Instead of the check valve 124 a very small bleed orifice 154 is provided in a wall oftube 114, which could also comprise a small 108, 112, 114 and 144. This is desirable so that the valve 116 can be normally closed while frost forms, and moves againstl the frost only occasionally to feel the same, thereby sensing its thickness. If the valve'were held open continuously, for example by a continuous supply of pressure in the air circuit, the frost might form around the valve and hence it would not be able to sense the frost thickness, which must `be done by periodic excursions of the valve against the frost while it forms.

FIG. 7 shows a modification of a portion of FIGS. 1 and 3, 3a, in which like elements bear like reference numerals. In FIGS. 7, the vacuum tube 31 communicates with a sealed chamber 156 of a bellows 158. Thus when the compressor starts, vacuum is produced in tube 31 notch on the seat for valve 116. Then when the door small bleed orifice 154. In FIG. 6, another modification of the frost-sensing means is illustrated which includes an extension 116e for the valve 116. In this construction,

the valve 116 is positioned farther above tube 30 so that its extension116a is set a predetermined distance T above the Y tube 30 (when valve 116 is normally closed). The advantage of this construction is that the periodic air bleed through valve 116 will not prevent normal formation of frost on tube 30; and, also, no frost can form at the valve itself.

In the forms of the invention shown in FIGS. 3, 3a, 5 and 6, the defrosting action is initiated by the first normal door opening following the build up of frost to a predetermined thickness T. The forms of the invention disclosed in FIGS. 7-11a utilize energy associated with the normal cycling of the compresssor to provide a periodic source of fluid pressure. In these forms of my invention the defrosting action is started at a 'compressor cycle following the build-up of frost to the predetermined thickness T. In the form ofthe invention in which the valve '116 senses the formation ofV frost, it is necessary that the pressure is'produced only periodically in the air circuit and chamber 156 causing bellows 158 to contract. This action causes the diaphragm 136, which is secured tothe free end of bellows 158, to compress air in chamber 144 the pressure of which is transmitted to chamber 108 through passage 112 to activate unit 15 as before when suficient frost is formed on tube 30. The pressure portion of the refrigerant circuit could =be used instead of vacuum by rearranging the bellows and diaphragms Without changing the scope of this concept. Y

FIG. 8 shows another modification of FIGS. l and 3,

3a, in which like elements are indicated by like reference chambers 108, 112 and 144 in FIGS. 3, 3a. A snap-action Y bimetal member, such as a bimetal disk 166, is held in a circular groove formed in spacer 162 and a cover 168. The disk 166 is connected to actuate diaphragm 136 through a shaft 170. The (cover `168 forms a chamber 172 which includes an electric resistance heating element 174 and insulating liners 176 for heating the bimetal disk. The electric circuit may be modified from that in FIG. 1 with the addition of heater 174energized through a wire 175, and the system operates as follows. When thermostat 58 is off, the compressor C, heater 174, and solenoid valve are all de-energized. When the thermostat switch 58 closes in normal operation, the compressor starts and heater 174 is energized. The heat energy Iproduced by element 174 causes the disk 166 and diaphragm 136 to snap to their most leftward positions for the purpose of converting heat energy to pressure energy. As described previously, without frost on tube 30, valve 116 opens at a low pressure energy to prevent sufficient pressure build-up for actuating diaphragm 102 and unit 15. But on the first compressor actuation following the formation of frost to a thickness T, pressure energy is built up by the disk snap-action to actuate diaphragm 102 and initiate unit 15. Then with arm 54 in the position 54', the compressor continues to run and solenoid valve S sends hot gas through the evaporator as described above. When all the frost has melted, the arm 54, shaft and diaphragm 102 snap back into the positions shown regardless of the position of the disk, since air can now be exhausted through Valve 116.'For this form of the invention, itis desirable to provide a snapaction to diaphragm 136 so that the pressure energy willV Y build up in chamber 164, even though valve 116 might leak slightly, or if orifice 154 is used. Any conventional bimetal snap-action element may be used, such as a cantilever type bimetal member, to actuate diaphragm 136, so that the disk type of snap action element 166 is merely shown by Way of illustration.

FIG. 9 shows a modification of the form of my invention shown in FIG. 8 except that the heater and bimetal disk is replaced by a solenoid. Also, by way of illustration, an electric heater type defrosting system is shown in place of the solenoid valve to bypass hot gas as in FIGS. 1, 8 and 11. It is important to appreciate that any of the defrosting systems and electric circuits may be operated by any form of my control invention disclosed herein, as well as other commonly used circuits not discussed. In

13 FIG. 9, elements common to those in FIGS. 1, 2, 3, 3a and 8 are indicated by the like reference numerals. Dia phragm 136 is clamped between spacer 160 and a cover 178 to which an electro-magnet or solenoid 180 is secured by suitable means. The solenoid comprises a coil 182 and an armature 184 operatively connected to diaphragm 136, as by a shaft, to effect movement thereof. A spring 186 is mounted in chamber 164 and retained by an abutment 18S to act on diaphragm 136 to oppose the force of armature 184. The electric circuit is slightly modified so that the compressor and solenoid 180 are off when thermostat switch S is open, an da defroster heater 190 is also off since it is connected to the normally open terminal 44. When the thermostat switch 58 closes, the compressor and solenoid 180 are energized so that armature 134 moves diaphragm 136 quickly to the left. This action has no effect on diaphragm 102 and unit 15 if no frost is formed on tube 30. However, when frost forms on tube 30 to a thickness T, the next closure of switch 58 causes unit 15 to be activated in a manner described above to start the defrosting action. At this time the compressor is turned olf while the heater 190 is energized to melt the frost, which is terminated by unit 15 as before.

FIG. 10 illustrates a modied form of the invention shown in FIG. 8 in which a fiat cantilever bimetal element 200 is used with the electric heater 174 of FIG. 8, and the desired snap action is provided solely by mechanical means. In FIG. 10, elements common to those in FIGS. l, 2, 3, 3a and 8 are indicated by the like reference numerals. yReferring to FIG. l0, diaphragm 136 is biased leftwardly by a spring 192 with sufficient force to overpower the force of spring 53 (FIG. 2). Diaphragm 136 has secured thereto a latch or detent member 194 biased downwardly by a leaf spring 196 secured to a cover 198. The detent member includes a catch portion disposed tO engage the end of the cantilever bimetal element 200, as shown, which is fixed at its other end. The detent member 194 also includes a cam portion disposed to engage a fixed cam 204. In operation, when the heater 174 (which is coiled around bimetal element 200) is energized the bimetal element engages the detent to overpower spring 192 and move the diaphragm 136 and detent to the right. After a predetermined travel, the detent strikes cam 204 and is lifted free of the bimetal element so that spring 192 snaps diaphragm 136 and detent 194 to the left which initiates unit only when frost has formed on coil 30, as described above. The rest of the operation is the same as described for FIG. 8. When the heater 174 is de-energized, the bimetal element 200 slowly moves to its inactive dotted position to again engage the latch projection of detent 194.

FIG. 10a illustrates a modification of the form of my invention shown in FIG. lO in that a bellows 206 is sealed and filled with a gas such as air or nitrogen to expand when heated by the electric heater 174 inside the bellows and controlled by the thermostat 58. An arm 208 which is hinged at one end to a fixed support replaces the bimetal element 200 but engages the projection of latch detent 194. The construction otherwise operates in the same manner as the apparatus shown in FIG. l0, such that when the heater 174 is energized, the bellows expands to carry arm 208, detent 194 and diaphragm 136 to the right until release of the detent is effected by cam 204. If desired, bellows 206 may actuate diaphragm 136 directly, or replace diaphragm 136.

The apparatus shown in FIGS. l1 and 11a is similar to the apparatus shown in FIGS. 9 and 10a except that a force-amplifying mechanism, such as a ratchet and cam mechanism, is interposed between the actuating element and diaphragm 136 in order to reduce the required size and force of such actuating element as ywell as reducing the source energy required. Broadly, this reduction in the size of the actuating element and the energy required therefor is to provide such a force-amplifying mechanism which integrates and stores the small energy over an extended period of time; and means are provided to release this stored energy at the end of this time period to provide a substantially larger actuating force than possible without the integrating mechanism.

Referring to IFIG. 1l, elements common to previous figures are indicated by like reference numerals, and the electric circuit is the same as illustrated in FIG. 8. In FIGY ll, the cantilever bimetal element 200 comprises the actuating or power element; this bimetal element is fixed at one end to support 202 and is free at its other end to move from a stop 210 to a stop 212 as electric heat energy is intermittently applied by a coil 174, controlled by the thermostat 58 in the form shown. The integrating mechanism' includes the following elements: A ratchet arm' 214, vwhich is hinged to the free end of bimetal strip 200 and biased downwardly by a spring 216 is moved by the bimetal 200 to engage and move one tooth 218`of a ratchet wheel 220. Reverse rotation of the wheel is prevented by a leaf spring pawl 222 secured to a fixed support 224. A spiral shaped cam 226 having a step 227 is operatively connected to wheel 220 for rotation therewith by shaft means 228, which is journaled by any suitable bushing means 230. A lever arm 232 is fulcrumed at a support 234 and actuates diaphragm 136 through a shaft 236. The integrated energy of the small bimetal strip 200 is stored in a spring 238 which acts on lever 232 with a force that can always overpower the force of spring 53 (FIG. 2) and causes the upper end of the lever to ride on the surface Of cam 226.

The device shown in FIG. l1 operates as follows: In the form shown, each normal compressor cycle causes a small wattage to energize heater 174 to revolve the ratchet wheel one tooth-length. After a number of compressor cycles (or equivalent intermittent energizing of heater 174) corresponding to one less than the number of teeth of wheel 220, the cam 226 arrives at the position shown. At the next energization of heater 174, as produced in the example shown by the next compressor cycle, spring 238 causes the end of lever 232 to snap over step 227 to the smallest radius of cam 226 to release the energy stored in spring 238 by intermittent heater 174. This action enables the actuator elements, 232, 236 and 136 to provide a large intermittent force to initiate the defrost action when called for. In the form shown, the lever 232 snaps diaphragm 136 to the left thereby converting the spring energy to pressure energy which initiates unit 15 to defrost only when sufiicient frost has formed on tube 30, all in a manner described above. FIG. lla shows merely that the ratchet 220 can be actuated by the solenoid shown in FIG. 9 which is operated at each compressor cycle instead of the bimetal and heater illustrated in FIG. 1l. A Spring 240 biases armature 184 leftwardly, but the rest of the operation of the form shown in FIG. 11a is the same as for FIG. 11. The advantage of this integrating mechanism is that the required size of the bimetal element 200 and heater element 174, as well as the source of energy therefor, can be reduced somewhat inversely as the number of teeth of ratchet 220. This is true since spring 238 can be charged or cocked in eight steps (as illustrated), for example, instead of one step as for the form of FIGS. 9 or 10.

Having now described my invention, it is important to appreciate that the defrosting control system disclosed herein for domestic refrigerators may be applied equally well to control ice thickness in commercial refrigeration, air conditioning, heat pumps, soft drink coolers or any other device for sensing and controlling the formation and/or melting of ice. Also the control invention has been illustrated using air pressure to actuate the diaphragm 102; but the inventive concepts would be unchanged if any fluid under pressure or vacuum were used in the fluid circuit by reversing or rearranging the diaphragm and its associated circuit.

' made without departing from the In its broadest aspect, the control device of the present invention can oe used in any application in which any substantially rm or solid material is subjected to a change in shape such as in its size, height, depth, thickness, etc., of its bulk or mass, and in which device means are provided to sense such change in shape (or to detect the presence or absence of such mass or body) to control the bnlk of said material to any predetermined value. In those instances in which a mass is in one place at one time but is not present at another time, such changes can also be sensed by the control device of the present invention. Other uses and modifications of the invention may be spirit and scope of the appended claims.

What I claim is:

1. In a device for controlling a variable condition of operation of a refrigerating machine, the combination of; control means to effect a change in said condition, a fluid circuit including means to produce intermittently a liuid pressure therein, movable pressure responsive means communicating AWith said circuit and being operatively connected to said control means for actuation thereof in response to a change in said intermittent pressure in said circuit; sensing means subjected to said controlled condition and having a movable portion operatively associated with said circuit andV disposed to enable said fluid pressure to escape and dissipate from said circuit at one variation of said controlled condition so that said pressure responsive means is not operated, and to contain said uid pressure in said circuit at another variation of said controlled condition to enable said movement of said pressure responsive means for actuating said control means.

2. In a device for controlling a variable condition of operation of a refrigerating machine, the combination of; control means to cause a change in said condition, an air circuit including means to produce intermittently an air pressure therein, movable pressure responsive means communicating with said air circuit and being operatively connected to said control Vmeans for actuation thereof in response to a change in said intermittent circuit pressure; sensingmeans subjected to said controlled condition and including movable valve means operatively associated with said circuit and affected by said condition for enabling said air pressure to escape and dissipate from said circuit to the atmosphere at one variation of said controlled condition so that said pressure responsive member is not operated, and to contain said air pressure at another variation of said controlled condition to enable said movement of said pressure responsive means for actuating said control means.

3. In a device to control an operating condition of a refrigerating machine in accordance with the formation of ice therein, the combination of; control means to effect a change in said operating condition, an aircircuit including means to produce an air pressure therein, movable pressure responsive means communicating with said circuit and being operatively connected to said control means for actuation thereof in response to a change in said circuit pressure, sensing means operatively associated with said circuit to detect the formation and melting of ice Within said refrigerating machine and including movable means for enabling said air pressure to escape and dissipate from said circuit to the atmosphere prior to the formation of a predetermined quantity of said ice for precluding operation of said pressure responsive means, and said movable means being disposed to contain said air pressure in said circuit after said-predetermined quantity of ice-is formed to enable said movement of said pressure responsive means by said circuit pressure for actuating said control means.

4. In a defroster control device for a refrigeratingV machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to provide heat for melting said frost, the cornbination of; means to control the defrosting action of said defrosting means, a fluid circuit including means to produce a fluid pressure therein, movable pressure responsive means communicating with said circuit and being operatively connected to said control means for actuation thereof in response to a change in said circuit pressure, frost-sensing means operatively associated with said circuit to detect the formation and melting of frost at least on said cooling unit and including movable means directly affected by said frost for enabling said fluid pressure to escape and dissipate from said circuit prior to the formation of said frost to a pre-determined thickness for precluding operation of said pressure responsive means, and said movable means being disposed to contain said pressure in said circuit when said predetermined thickness of frost is formed to ena-ble said movement of said pressure responsive means -by said circuit pressure for actuating said control means.

5. The combination of means defined in claim 4, and a termination sensing member having a portion disposed to abut some ice in said machine and normally disconnected from said control means, means adapted to cause operative connection of said control means and said sensing member substantially upon said actuating movement of said pressure responsive means for initiating a melting .action of said frost, force-producing means acting on said control means upon said actuating movement of said pres-V sure responsive means to cause said then-connected sensing member to abut against said ice tending to compressV the ice against a xed abutment in said machine and gradually move with said ice as it progressively melts and including means to etfect a termination of said melting7 action.

6. The combination of elements defined in claim 4, in which said pressure responsive means includes exible diaphragm means.

7. The combination of elements defined in claim 4, in which sa-id pressure responsive means includes a rst ilexible diaphragm member, and said pressure-producing means includes a second exible diaphragm member, and means to periodically reciprocate said second diaphragm member to produce said fluid pressure in said circuit.

8. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to provide heat for melting said frost, the cornbination of; means to control the duration of said defrosting means, an air circuit including means to produce an air pressure therein, movable pressure responsive means communicating With said circuit and being operatively connected to said control means for actuation thereof in response to a change in said circuit pressure; frost sensing means operatively associated with said circuit to detect the formation and melting of frost at least on said cooling unit and including movable means to periodically feel said frost for enabling said air pressure to escape and dissipate from said circuit to the atmosphere in one positionk of said movable means prior to the formation ofsaid frost to a predetermined thickness for precluding operat-ion of said pressure responsive means,and saidV movable means being disposed to contain said pressure in said circuit at another position of said movable means when said predetermined thickness of frost is formed to enable said movement of said pressure responsive means by said circuit pressure for actuating said control means.

9. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon 'and including normally inactive defrosting means to provide heat for melting said frost, the combination of; means to control the defrosting action of said defrosting means, a uid circuit, pressure-producing means associated with said circuit Vto provide a periodic fluid pressure therein, movable pressure-responsive means communicating with said circuit and being operatively connected to said control means for actuation thereof in response t0 Said periodic pressure `in said circuit, frostsensing means including normally closed valve means having a movable valve member to control the uid pressure in said circuit, means to mount said movable valve means at a predetermined distance from a portion of said cooling unit for periodically feeling said frost and enabling said valve member to open and dissipate said periodic pressure from said circuit prior to the accomulation of said frost to a predetermined thickness, said valve member being progressively blocked against said opening movement by frost accumulating to said predetermined thickness to contain said periodic pressure in said circuit for enabling said movement of said pressure responsive means by said circuit pressure to actuate said control means.

10. The combination of means defined in claim 9, and a termination sensing member having a portion disposed to abut some ice in said machine and disconnected from said control means during normal operation of said machine, means to operatively connect said control means to said sensing member upon said actuating movement of said pressure responsive means for initiating said defrosting action, biasing means acting on said control means to cause said then-connected sensing member to abut against said ice tending to compress same between said sensing member and a fixed abutment in said machine and to move with said ice as it progressively melts to form a thermally-varying frozen-liquid link between said sensing member and said abutment to sustain said defrosting action, means to effect a disengagement of said operative connection after a predetermined travel of said sensing member during said last-named movement, said -biasing means then returning said control means to its original position corresponding to said normal operation of said machine for terminating said defrosting action, and means to return said sensing member upon said disengagement to its original position.

11. The combination of elements defined in claim 8, in which said fluid comprises air from the atmosphere, and means for enabling air to be drawn into said circuit between said periodic intervals of pressure therein to charge said circuit.

12. In a defroster control device for a refrigerating machine having a cooling unit subject to t-he formation of frost thereon and including normally inactive defrosting means to provide heat for melting said frost, said refrigerating machine including a compartment containing said cooling unit and door means forming a wall of said compartment, the combination of; means to control the defrosting action of said defrosting means, a fluid circuit including means to produce a'uid pressure therein, said pressure-producing means including a reciprocating member comprising a movable wall of a pressure chamber in said fluid circuit, actuating means operatively connecting said door means to said movable wall for effecting said reciprocating movements thereof incident to normal opening and closing movements of said door means, movable pressure responsive means communicating with said circuit and ibeing operatively connected to said control means for actuation thereof in response to a change in said circuit pressure, frost-sensing means to detect the formation and melting of frost at least on said cooling unit and including means directly affected by said frost for enabling said fluid pressure to escape and dissipate from said circuit prior to the formation of said frost to a predetermined thickness for precluding operation of said pressure responsive means, and said sensing means being disposed to contain said pressure in said circuit when said predetermined thickness of frost is formed to enable said movement of said pressure responsive means for actuating said control means.

13. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to provide heat for melting said frost, said refrigerating machine including a compressor driven by an electric motor connected in an electric circuit having -a temperature-controlled switch .therein to control each cycle of said motor and compressor, the combination of, means to regulate the defrosting .action of said defrosting means, `a fuid circuit including means to produce a fluid pressure therein, said pressure-producing means including a reciprocating member comprising a movable wall of a pressure chamber in said fluid circuit, actuating means having means connected in said electric circuit and operatively connected to said movable wall for effecting said reciprocating movements thereof as a function of the cycling of said compressor and motor, movable pressure responsive means communicating with said circuit and being operatively connected to said regulating means for actuation thereof in response to a change in said circuit pressure; frost sensing means subjected to formation and melting of frost at least on said cooling unit and including means directly affected by said frost for enabling said fluid pressure to escape and dissipate from said circuit prior to the formation of a predetermined amount of said frost, whereby said pressure responsive means is not operable, and to contain said pressure in said circuit when said predetermined amount of frost is formed to ena-ble said movement of said pressure responsive means for actuating said regulating means.

14. The combination of elements defined in claim 13, and a ratchet mechanism disposed to count the number of compressor cycles and interposed between said actu-ating means and said movable wall to effect intermittent pressure-producing movement thereof upon a predetermined number of compressor cycles.

15. ln a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to provide heat for melting said frost, and an elect-ric circuit having a source lof electrical energyvoperatively associated with said refrigerating machine, the combination of; means to control the duration and termination of said defrosting means, means to initiate operation of said control means including energy-storing spring means adapted to be operatively connected to said control means for periodic actuation thereof, said initiating means including a force-amplifying movable cam means, cam-follower means operated by s-aid cam means and adapted to be operatively connected to said spring means for -gradual periodic actuation thereof for storing energy therein while said control means is operatively disconnected from said spring means and said c-am means, ratchet means operatively connected to said cam means for operation thereof and having a predetermined nurnber of ratchet teeth, electrically powered ratchet actuating means including intermittently operated switch means connected in said electric circuit to periodically provide electrical energy for causing movement of said ratchet means a predetermined amount upon each cycle-operation of said switch means, means to enable said operative connection of said spring means and said control means after a predetermined travel of said cam means, and said cam means including means to cause a release -of said energy stored in said spring means upon said predetermined travel of said cam means to cause said initiation of said control means after a predetermined number of cycles of said switch means.

16. The combination of means dened in claim 15, and said electrically powered ratchet actuating means including bimetal means and electric heating means near said bimetal means controlled by said intermittently operated switch means for causing reciprocating movements of said -bimetal means corresponding to said periodic provision of electrical energy, said ratchet means including a rotating ratchet member having a plurality of ratchet teeth, said ratchet actuating means also including a ratchet actuating element cooperating with said teeth and operated as a result of said movement of said bimetal means to cause a predetermined movement of said ratchet member upon each said periodic movement of said bimetal means, and said ratchet means yalso including a paWl cooperating with said teeth to prevent reverse rtation of said ratchet member, and said release means of said cam means comprising a step in the surface of said cam means to enable sudden movement of said follower means as a result of the stored energy of said spring means after a predetermined travel of said cam means.

17. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to provide heat for melting said frost, said refrigerating machine also including a compressor driven by an electric motor connected in an electric circuit having a temperature-controlled switch therein to control eac-h cycle of said motor and compressor, the combination of; means to control the duration and termination of said defros-ting means, mechanism to initiate the operation of said control means including energy-storing means adapted to be operatively connected to said control means for periodic actuation thereof, said initiating mechanism including cam means, means operated by said cam means and operatively connected to said energystoring means for actuation thereof for storing energy therein while said control means is operatively disconnected from said energy-storing means and said cam means, ratchet means operatively connected to said cam means having a predetermined number of ratchet teeth, ratchet-actuating means including means connected to said electric circuit for moving said ratchet means a predetermined amount upon each cycle of said compressor as controlled .by said temperature cont-rolled switch, and said cam means including means to cause only said initiation of operation of said control means after a predetermined number of compressor cycles.

18. In a control `device for a mechanism having a surface subject to the formation thereon of a freezable and meltable material, the combination of; control means for causing a change in the quantity of said material forming on said surface, initiating means to periodically cause operation of `said cont-rol means when said material has formed to an undesirable quantity on said surface, a source of energy, power means operated by said energy source and operatively associated with said initiating means to provide a small input power force, force-amplifying means operated by said power means to integrate and store said energy over a period of time while said control means is operatively disconnected from said initiating means for providing an amplified output force substantially larger than said input power force available to cause operation of said initiating means, and said -amplifying means including means to release said stored energy after said period of time to produce said amplified output force for operating said initiating means.

19. In a control device associated with apparatus having a surface subject to the formation of frozen but meltable substance adjacent thereto, the combination of; means to control the amount of said frozen substance, actuating means disposed to cause operation of said control means after said substance has formed to a predetermined amount, sensing means dependent on the formation of said frozen su-bstance to preclude said actuating means from operating said control means when said formation of said frozen substance is less than said predetermined amount, said sensing means including means to enable said actuating means to be operatively connected to said control means for operation thereof after the said frozen substance has formed to substantially said predetermined amount, intermittent energy means associated with said device to provide periodic force impulses, a ratchet mechanism disposed to count the number of said periodic force impulses and interposed between said ene-rgy means and said actuating-means to cause intermittent movements thereof, and said Iathet mechanism including energy-integrating means providing amplified forces larger than said force impulses and acting on said -actuating means upon the occurrence of a predetermined number of said impulses.

20. In a control device for a mechanism having a surf-ace subject to the formation thereon of a freezable and meltable material, the combination of; control means for causing a change in the quantity of said material forming on said surface, initiating means to periodically cause operation of saidcontrol means when said material has formed to an undesirable thickness on said surface, a source of energy, power means operated by said energy source and operatively associated with said initiating means to provide a small input power force, forceamplifying means operated by said power means to integra-te and store said energy over a period of time for providing an amplified output force substantially larger than said input power force available to cause operation of said initiating means, said amplifying means including means to release said stored energy after said periodof time to produce said amplified output force for operating said initiating means, said initiating means including sensing means operable to detect the formation of said material on said surface to said undesirable thickness for enabling said output force to operate said control means upon operating said initiating means, and means producing a sensing force considerably less in magnitude than and independent of said actuating force to cause said detectingoperation of said sensing means.

21. In a control device for a mechanism having ya surface subject to the formation thereon of a freezable and meltable material, an elect-ric circuit associated with said mechanism, the combination of; control means for causing a change in the quantity of said material forming on said surface, initiating means to periodically cause operation of said control means when said material has formed to an undesirable quantity on said surface, a source of energy, power means operated by said energy source -and operatively associated with said initiating means to provide a small input power force, force-amplifying means operated by said power means to integrate and store said energy over a period of time while said control means is operatively disconnected f-rom said initiating means for providing an amplified output force substantially larger than said input power force available to cause operation of said initiating means, said amplifying means including means to release said stored energy after said period of time to lproduce said amplified output force for operating said initiating means, said power means including a :bimetallic element, an electric heating element connected in said electric circuit and mounted adjacent said bimetallic element to heat same for effecting said operation of said power means, and periodically operated switch means in said circuit to provide intermittent heating and cooling of said bimetallic element to effect alternating movement thereof.

Z2. The combination of means defined in claim 21, in which said force amplifying means includes a movable cam operated slowly by said alternating movements of said bimetallic element, and said force-amplifying means including spring means operated by said movement of said cam to store said energy for producing said amplied output force, and said means to release said stored energy comprising a step in said cam to enable said spring means to cause operation of said control means after a predetermined travel of said cam.

23. In a control device for a mechanism having a surface subject to the formation thereon of a freezable and meltable material, an electric circuit associated with said mechanism, the combination of; control means for causing a change in the thickness of said material accumulated on said surface, initiating means adapted to provide a relatively large actuating force for periodic operation of said control means when said material has accumulated to a predetermined thickness, movable thickness-sensing means operable to detect the accumulation of said material on said surface to said predetermined thickness for enabling said actuating force to operate said control means upon operating said initiating means, said sensing means including means producing a sensing force less in magnitude than and independent of said actuating force to cause said detecting operation of said sensing means, a bimetallic element operatively associated with said initiating means to cause said periodic actuating force provided thereby, an electric heating element connected in said electric circuit and mounted adjacent said bimetallic element to heat same, and periodically operated switch means in said circuit to provide intermittent heating and cooling of said bimetallic element to effect a-lternating operation thereof.

24. In a control device for a refrigeration machine having'a cooling surface subject to the formation of frost thereon, and an electric circuit associated with said machine, the combination of; control means for causing a change in the amount of said frost formed on said surface, initiating means operatively associated with said control means for causing operation thereof to start melting the frost formed on said surface, said initiating means including a gas-filled chamber having a flexible wall, an electric heating element connected in said electric circuit and mounted adjacent said gas-filled chamber to heat and expand same, periodically-operated switch means in said circuit to provide intermittent heating and cooling of said element for causing alternate operation thereof, and means to terminate the melting action of 4said control means, whereby the cycle can be repeated.

25. In a control device for a refrigeration machine having a cooling surface subject to the formation of frost thereon, and said machine including a refrigerant circuit containing gas at varying pressures, the combination of; control means for causing `a melting of said frost formed on said surface, initiating means operatively associated with said control means for causing operation thereof to start melting the frost formed on said surface, a reciprocating member for operating said initiating means comprising a movable wall of a chamber in said refrigerant circuit, said reciprocating member being responsive to changes of pressure in said circuit for effecting said reciprocating movements of said member, and means to terminate the melting action including termination sensing means contacting some ice, said termination means including force-producing means `.activated by said initiating means upon starting said melting action and disposed to act on said termination sensing means for causing same to abut against said last-named ice and gradually to move therewith as said ice progressively melts until said frostmelting action is terminated.

26. In a control device for a mechanism having a surface subject to the formation thereon of a freezable and meltable material, an electric circuit associated with said mechanism, the combination of; control means for causing a change in the quantity of said material forming on said surface, initiating means to periodically cause operation of said control means when said material has formed to an undesirable quantity on said surface, a source of energy, power means operated by said energy source and operatively associated with said initiating means to provide a small input power force, force-amplifying means operated by said power means to integrate and store said energy over a period of time while said control means is operatively disconnected from said initiating means for providing an amplified output force substantially larger than said input power force available to cause operation of said initiating means, said amplifying means including means to release said stored energy after said period of time to produce said amplified output force-for operating said initiating means to cause said periodic operation of said control means, said power means including electrically operated means connected in said electric circuit, and periodically operated switch means in said 22 circuit to provide intermittent energization of said electrically operated means to effect alternating operation thereof.

v27. The combination of elements defined in claim 26, in which said power means comprises a bimetal element, and an electric heating element connected in said electric circuit and mounted adjacent said bimetal element to heat same for effecting said alternating operation.

28. In a control device for a refrigeration machine having a surface subject to the formation thereon of a freezable and meltable material, said machine including a source of electrical energy in a rst form thereof, the combination of; control means for causing a change in the depth of said material supported by said surface, means providing intermittent pulses of said electrical energy and including b'imetallic means reciprocatingly movable in response to said pulses to convert said source energy to a second form of energy different from said first form of energy, sensing means operatively associated wtih said bimetallic means and movable in response to changes in forces produced by changes in the amount of said second form of energy to move toward and away from a portion of said surface for detecting the formation of said material thereon when the depth is less than a predetermined amount, actuating means operatively associated with said control means and including a member adapted to be movable in response to changes in the amount of said second form of energy to produce forces acting on said control means for operation thereof, and said sensing means including means to abut said material for enabling same to restrict said sensing movements when the material has formed to said predetermined depth for causing said movements of said actuating means as a result of said changes in the amount of said secon form of energy.

29. The combination of means delined in claim 28, in which said freezable material comprises frost formed on `a cooling surface of said machine, and melting mean-s operated by said electrical energy to provide heat near said cooling surface for melting said frost, and said control means comprising first switch means for controlling said electrical energy to said melting means, electric heating means mounted near said bimetallic means for providing periods of heat caused by said intermittent pulses of electrical energy for effecting said reciprocating movements thereof, and said means providing said intermittent pulses of electrical energy including second switch means periodically operated for causing said periods of heat.

30. In la device for controlling a variable condition of operation of a refrigerating machine, the combination of; control means to effect a change in said condition, a fluid circuit including means to produce intermittently a fluid pressure therein, movable pressure responsive means communicating with said circuit and being operatively connected to said control means for actuation thereof in response to a change in said intermittent pressure in said circuit, sensing means subjected to said controlled condition and having a movable portion operatively associated with said circuit and disposed to enable said fluid pressure to escape and dissipate from said circuit at one variation of said controlled condition so that said pressure responsive means is not operated, and to contain said fluid pressure in said circuit at another variation of said controlled condition to enable said movement of said pressure responsive means for actuating said control means, and means to terminate said change in said condition including termination sensing means contacting some ice in said machine subjectable to said condition for causing a melting thereof, force-producing means activated upon said actuation of said control means for starting said change in said condition and disposed to act on said termination sensing means for causing same to abut against said ice and gradually to move therewith as said ice gradually melts until sufficient ice has melted Z3 for effecting 4a. termination of said change in said condition.

References Cited UNITED STATES PATENTS 2,123,073 7/1938 Bell 62-140 2,229,181 1/ 1941 Leilich 62-140 2,711,079 6/1955' Grimshaw 62-154 X Z4 IRaney 62-140 Judd 62-154 X Thorner 62-154 X Evarard 62-154 Iokela 642-740 ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

